Antibodies to CNTN1/CASPR1 complex are described rarely in patients with chronic immune-mediated demyelinating polyradiculoneuropathy (CIDP), presenting with a severe neuropathy and ataxia. We present a case with a 17-year, relapsing-remitting course, expanding the evolving phenotype.

A 56-year-old woman presented in 2003 with a three-month history of progressive dysaesthesia in her hands and gait ataxia. CSF protein was over 2g/L. Nerve conduction studies demonstrated delayed median and tibial F-wave latencies consistent with a polyradiculopathy. A diagnosis of CIDP was made. Transient improvement was noted following IVIG, but symptoms relapsed again after 10 days. At nadir, four months from onset, she was wheelchair-bound with severe proprioceptive loss, cardiovascular dysautonomia, allodynia and sensory ataxia. Following repeated courses of IVIG and introduction of azathioprine with weaned steroids, she regained normal function after a further six months.

Mild, sensory relapses, in the absence of infection, occurred in 2009 and 2015 with complete resolution of symptoms and examination normalisation during remission. Maintenance treatment on reduced-dose azathioprine (50mg od) was continued until March 2020.

In July 2020, our patient reported minimal recurrence of dysaesthesia in her finger tips which progressed over three weeks. Examination showed areflexia, asymmetric ptosis, marked loss of proprioception and vibration throughout, with gait ataxia.

Median F-wave latencies were persistently delayed, and tibial F-wave latencies were now unrecordable.

IgG antibodies directed against CNTN1/ CASPR1 complex were identified using cell-based-assay and ELISA.

Treatment with IV steroids was initiated, but due to continued clinical deterioration over five days, IVIG  was commenced (0.4g/kg/day for five days). Mycophenolate mofetil was introduced. Transient improvement for two weeks was noted but not sustained, as in 2003.

We present a 73-year-old woman with a seventeen-year relapsing-remitting course, most likely due to anti-CNTN1/CASPR1 complex antibody-associated CIDP, characterised by stereotyped, biphasic, sensory relapses of variable severity and full recovery between episodes.